A built-up exhaust valve is one in which （）.

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  A . Bad combustion of the fuel B . Bad atomization of the fuel C . Liquid contaminants D . Solid contaminant

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• For an ordinary four-stroke engine the exhaust valves open （）.

  A . after TDC B . before TDC C . after BDC D . before BDC

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• Exhaust temperature increases in all cylinders, the possible cause may be（） (1) increased scavenging air temperature (2) air in fuel pumps and fuel valves (3) fouling of air and gas passages

  A . (1)+(2) B . (1)+(3) C . (2)+(3) D . (1)+(2)+(3)

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• A patient suffering from heat exhaustion should be（）.

  A . moved to a cool room and told to lie down B . kept standing and encouraged to walk slowly and continuously C . given a glass of water and told to return to work after 15 minutes of rest D . None of the above are correct

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• During the valve overlap period, the exhaust pressure of a turbochargers, four-stroke/cycle diesel engine must be less than the intake manifold pressure to ensure （）

  A . effective cylinder scavenging and cooling B . constant pressure from the turbochargers C . cooler operation of the exhaust system D . effective constant pressure for turbocharger operatio

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• Now that the valve is not worth （）, I suggest it （）.

  A . to repair；to renew B . repairing；be renewed C . repairing；will be renewed D . to repair；to be renewed

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• In an engine with air inlet valve and exhaust valve on its cylinder heads the fresh air will enter into the cylinder （） and the gases exhaust （）, there being an adequate overlap between the inlet opening and the exhaust closing.

  A . downwards；upwards B . upwards；downwards C . downwards；downwards D . upwards；upward

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• A two-stroke diesel engine exhaust temperature will be lower than a four-stroke diesel engine of the same displacement because the （） (1) MEP is lower and the scavenging air is cooling the exhaust gases (2) valve overlap in a four-stroke

  A . (1) only is correct B . (2) only is correct C . both (1) and (2) are correct D . Neither (1) or (2) are correct

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• The exhaust valve opens before bottom dead center in a four stroke engine to（） Ⅰ.allow for blow down Ⅱ.Reduce pumping losses

  A . Ⅰ only B . Ⅱ only C . both Ⅰ and Ⅱ D . neither Ⅰ nor Ⅱ

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• A two-stroke diesel engine exhaust temperature will be lower than a four-stroke diesel engine of the same displacement because the （） (1) scavenging air is cooling the exhaust gases (2) exhaust cycle time is longer

  A . (1) only B . (2) only C . both (1) and (2) D . neither (1) nor (2)

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• The satisfactory operation of diesel engine exhaust valves usually depends on（）

  A . the proper back pressure B . the cooling water temperature C . correct timing and proper seating D . accurate metering and the exhaust temperature

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• The opening of an exhaust valve on a modem, large, low-speed, main propulsion diesel engine may be actuated by （）.

  A . direct action of cam shaft B . compressed air pressure C . hydraulic “push rods” D . direct action of the main piston moving dow

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• If the engine is naturally aspirated, or is a small high-speed type with a centrifugal turbocharger, the period of valve overlap（）,ie when both valves are（）, will be and the exhaust valve will close some 10°top dead canter（）.

  A . open；short；after B . closed；short；after C . open；long；before D . closed；long；before

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• For an ordinary four-stroke diesel engine the exhaust valves close （）.

  A . after TDC B . before TDC C . after BDC D . before BDC

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• A substance found in residual fuels which tends to cause exhaust valve corrosion and grooving, is（）

  A . carbon B . vanadium C . calcium D . hydroge

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• A diesel engine emits blue exhaust smoke as a result of（）

  A . cold intake air B . excessive compression pressure C . excessive cylinder lubrication D . a light load

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• In a diesel engine, exhaust valves open before the intake ports are uncovered to （） Ⅰ.reduce pumping losses Ⅱ.reduce back pressure

  A . Ⅰonly B . Ⅱonly C . bothⅠand Ⅱ D . neitherⅠnor Ⅱ

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• Exhaust valve openings in a diesel engine cylinder head are made as large as practical to （）

  A . increase back pressure during the exhaust process B . facilitate periodic replacement of the valves C . reduce the pumping loss associated with scavenging D . reduce tension on valve spring

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• Leaky exhaust valve will result in which of the following?（） (1) high exhaust temperature; (2) low compression pressure; (3) low firing pressure.

  A . (1) and (2) B . (1) only C . (2) only D . (1),(2) and (3)

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• In an ordinary four-stroke engine the exhaust valves open （）

  A . after TDC B . before TDC C . after BDC D . before BDC

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• 听力原文：W: I am totally exhausted. I stayed up the whole night studying for the final examination.

  M: What have you done during your previous study time？ Q: What does the man imply？ (13) A．She has wasted much study time. B．She sleeps too much. C．Staying up is bad for health. D．She is an excellent student.

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• Leaky exhaust valve will result in which of the following？①high exhausttemperature ②low compression ③low firing pressure

  A.① and ② B.② and ③ C.① ② and ③

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• In a turbocharged four-stroke/cycle diesel engine, the exhaust valve remains open until after top dead center and the intake valve opens before top dead center to_______.

  A.produce a scavenging effect in the combustion space B.equalize cylinder and exhaust manifold pressures C.alleviate the difference in valve size between the intake and exhaust D.flush out condensate that collects after each compression stroke

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• The exhaust valve opens before bottom dead center in a four stroke engine to______Iallow for blow down IIReduce pumping losses

  A.I only B.II only C.both I and II D.neither I nor II

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